Ethanol and Acetaldehyde

1 Ethanol and Acetaldehyde. - Alcohol dehydrogenase (ADH) and cytochrome P4502E1 (CYP2E1) oxidise ethanol to acetaldehyde, which is further oxidised to acetate by aldehyde dehydrogenase (ADH). Acetaldehyde has been considered to play a key role in the toxicity of ethanol, primarily through its formation of covalent adducts (Schiff bases) with proteins, thereby provoking an immunotoxic response. More recently, attention has focussed on the role of the a-hydroxyethyl radical, which also forms protein adducts that elicit im-munotoxicity.  

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Among the other chemicals prepared from ethylene are ethanol and acetaldehyde... 

Reactions with Alcohols, Mercaptans, and Phenols. Alcohols add readily to acetaldehyde in the presence of trace quantities of mineral acid to form acetals eg, ethanol and acetaldehyde form diethyl acetal [105-57-7] (65). Similarly, cycHc acetals are formed by reactions with glycols and other polyhydroxy compounds eg, ethylene glycol [107-21-1] and acetaldehyde give 2-methyl-1,3-dioxolane [497-26-7] (66) ... 

Oxidation of Hydrocarbons. Ethanol is one of a variety of oxygen-containing compounds produced by the oxidation of hydrocarbons. Ethanol is reported to be obtained in a yield of 51% by the slow combustion of ethane (158,159). When propane is oxidi2ed at 350°C under a pressure of 17.2 MPa (170 atm) (160,161), 8% of the oxygen is converted to ethanol. Lower conversions to ethanol are obtained by oxidi2ing butane. Other oxidation systems used to produce ethanol and acetaldehyde (162—164) and methods for separating the products have been described in the patent Hterature. 

During World War II, production of butadiene (qv) from ethanol was of great importance. About 60% of the butadiene produced in the United States during that time was obtained by a two-step process utilizing a 3 1 mixture of ethanol and acetaldehyde at atmospheric pressure and a catalyst of tantalum oxide and siHca gel at 325—350°C (393—397). Extensive catalytic studies were reported (398—401) including a fluidized process (402). However, because of later developments in the manufacture of butadiene by the dehydrogenation of butane and butenes, and by naphtha cracking, the use of ethanol as a raw material for this purpose has all but disappeared. 

Ethanol metabolism occurs mainly in the liver and proceeds by oxidation in two steps, first to acetaldehyde (CHjCHO) and then to acetic add (CH3CO2H)- When continuously present in the body, ethanol and acetaldehyde are toxic, leading to the devastating physical and metabolic deterioration... 

Smith BR, Amit Z The role of gamma-aminobutyric acid (GABA) in the regulation of ethanol and acetaldehyde self-administration. Prog Neuropsychopharmacol Biol Psychiatry 9 759-763, 1985... 

Lai SCS, Koper MTM. 2009. Electro-oxidation of ethanol and acetaldehyde on platinum single-crystal electrodes. Faraday Discuss 140 399-416. 

Perez JM, Munoz E, Moralldn E, Cases F, Vazquez JL, Aldaz A. 1994. Formation of CO during adsorption on platinum electrodes of methanol, formaldehyde, ethanol and acetaldehyde in carbonate medium. J Electroanal Chem 368 285-291. 

Both ADH and ALDH use NAD+ as cofactor in the oxidation of ethanol to acetaldehyde. The rate of alcohol metabolism is determined not only by the amount of ADH and ALDH2 enzyme in tissue and by their functional characteristics, but also by the concentrations of the cofactors NAD+ and NADH and of ethanol and acetaldehyde in the cellular compartments (i.e., cytosol and mitochondria). Environmental influences on elimination rate can occur through changes in the redox ratio of NAD+/NADH and through changes in hepatic blood flow. The equilib-... 

In any case acetic acid does occur, but in addition to it lactic acid and also some ethanol and acetaldehyde may be present. Schoen and Eras report that aldohexoses do not yield D-mannitol, while in addition... 

Kinetic parameters for the oxidation by stoich. [Ru(H30)(bpy)(tpy)] Vwater pH 7 of a number of carbohydrates and nucleotides were measured and are consistent with carbohydrate oxidation at the T position [668]. Electrocatalytic oxidations of 2-propanol to acetone, ethanol and acetaldehyde to acetate, p-xylene and /i-phthalate to terephthalate, cyclohexene to 2-cyclohexen-l-one and toluene to benzoate with the couple [Ru(0)(bpy)(tpy)] V[Ru"(H30)(bpy)(tpy)] Vwater pH... 

The addition of ethylene to a CO-H flow on a Rh-CeO catalyst (fig. 4), which should enhance the surface concentration of C H groups increased the formation of propanol and propionaldehyde and decreased the ethanol and acetaldehyde production. 

Action of Diethylamine on Decomposition of Ethyl tert-Butyl Peroxide. The rate of decomposition of ethyl ferf-butyl peroxide is decreased by adding diethylamine (Figure 7), and the yield of products is altered (Table II). Again, the yield of methane is increased at the expense of ethane and f erf-butyl alcohol is increased at the expense of acetone. Ethanol and acetaldehyde are formed in considerably greater amounts. The yields of carbon monoxide and methyl ethyl ketone are decreased. 

Related work has been reported in amide solvents with halide or hydro-halic acid promoters (196). Ethanol and acetaldehyde as well as methanol are observed. Enhanced yields of acetaldehyde appear to be obtainable by operating such a system at reduced temperatures, although overall rates of CO reduction suffer. 

Figure 6 Adsorption isotherms for (a) ethanol and acetaldehyde (from Ref. 49), and (b) toluene (From Ref. 50) on TiOi.

Barilyak. l.R. Kozachuk, S.Y. (1983) Embryotoxic and mutagenic activity of ethanol and acetaldehyde after intra-amniotic injection. Tsitol. Genet.. 17, 60-63 (in Russian)... 

Crebelli, R., Conti, G, Conti, L. Carere, A. (1989) A comparative study on ethanol and acetaldehyde as inducers of chromosome malsegregation in Aspergillus nidulans. Mutat. Res., 215, 187-195... 

Jansson, T. (1982) The frequency of sister chromatid exchanges in human lymphocytes treated with ethanol and acetaldehyde. Hereditas, 97, 301-303... 

Cho, K.-J. Jang, J.-J. (1993) Effects of carbon tetrachloride, ethanol and acetaldehyde on di-ethylnitrosamine-induced hepatocarcinogenesis in rats. Cancer Lett., 70, 33-39... 

Lin. Y.-C.. Ho. I.-C. Lee. T.-C. (1989) Ethanol and acetaldehyde potentiate the clastogenicity of ultraviolet light, methyl methanesulfonate. mitomycin C and bleomycin in Chinese hamster ovary cells. Mutat. Res.. 216. 93-99... 

Two types of inhibitors, pyrazoles and imidazoles (with E-NAD+) and iso-butyramide (with E-NADH), form tight ternary complexes with E-coenzyme, allowing single turnover to be observed (through photometry at 290 nm or fluorescence caused by NADH) and thus titration of the active sites (see Section 9.2.3.). Pyrazole and isobutyramide are kinetically competitive with ethanol and acetaldehyde, respectively. If the reaction E + NADH + aldehyde is run in the presence of a high concentration of pyrazole, the complex E-NAD+ formed by dissociation of alcohol immediately binds pyrazole for a single turnover only. Under favorable conditions, a single NADH oxidation can be observed by stopped-flow techniques to find a kcat of about 150 s 1 and a deuterium isotope effect kD 4 as expected (see Section 9.2.5). 

Both cell culture with a lipophilic extraction phase and with a polar extraction phase have been reported to be helpful for the accumulation and detection of secondary substances [7,8]. Plant cell cultures release lipophilic and volatile substances such as ethylene, ethanol, and acetaldehyde. The addition of a lipophilic phase to the culture medium can be used as a means of accumulating and detecting these substances. Maisch et al. [8] found that the addition of XAD-4 resin to Nicotiana tabacum cultures enhanced the production of phenolic secondary metabolites several times compared to the adsorbent-free control. Kim and Chang [9] reported in situ extraction for enhanced shikonin production by Lithospermum erythrorhizon. When n-hexadecane was added to the cultivation, higher specific shikonin productivity was obtained than that from the cultures of free cells without extraction. They also suggested that n-hexadecane addition at an early stage in calcium alginate immobilized cell cultures was effective for shikonin production. Most of the produced shikonin was dissolved in n-hexadecane, so it would reduce the costs for shikonin separation. 

This is probably because 0 atoms produced in primary process (45) react much more rapidly with C2H6 than with N20. Several products are formed including ethylene, butane, carbon monoxide, hydrogen, methane, and probably ethanol and acetaldehyde. More ethylene is formed than one would expect from the amount of butane. It was found that 0 atoms react rapidly with ethylene, which is one of the photolytic products. The reaction-rate constant of O atoms with ethylene is estimated to be about 330 times as rapid as that with ethane.82 Complete elucidation of the mechanism of O-atom reaction with ethane is complicated because of the rapid reaction of O atoms with one or more of the products. 

Sauer ML, Ollis DF (1996) Photocatalyzed Oxidation of Ethanol and Acetaldehyde in Humidified Air, J. Catal. 158 570-582. 

Using the catalyst system known from the Monsanto process, Dumas et at. have been able to direct the reaction towards ethanol formation using syngas mixtures extremely rich in hydrogen [87]. As is shown in Table XII, no acetic acid and only minor amounts of acetates are formed at an H3/CO ratio of 60. Ethanol and acetaldehyde aie the main products along with considerable amounts of methyl ethyl ether. Unfortunately, the Dumas c/ at. based the yields and conversion on carbon monoxide and not on methanol. This makes the data of this interesting process difficult to compare with those of other catalyst systems. 

The restrictive conditions of the biological aging process of wine (namely low pH, presence of sulphite, high ethanol and acetaldehyde concentrations, lack of sugars and low oxygen concentration) are compatible with only a few S. cerevisiae races. Also, the presence of specific flor races has been correlated with the aging stage of the wine and the sensory features of the end product (Mesa et al. 2000). 

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